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Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements. A dense, malleable, ductile, precious, grey-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. Platinum is used in jewellery, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and catalytic converters. Characteristics Platinum does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulphur, and caustic alkalis. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in aqua regia to form chloroplatinic acid, H2PtCl6. Platinum's resistance to wear and tarnish is well suited for making fine jewellery. The metal has an excellent resistance to corrosion and high temperatures and has stable electrical properties. All of these characteristics have been exploited for industrial applications Platinum's most common oxidation states are +2, and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. As is expected, tetracoordinate platinum(II) compounds tend to adopt a square planar geometry. While elemental platinum is generally unreactive, it dissolves in aqua regia to give soluble hexachloroplatinic acid ("H2PtCl6", formally (H3O)2PtCl6·nH2O ) This compound has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst. Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate, which is very insoluble in ammonium solutions. Heating the ammonium salt in the presence of hydrogen reduces it to elemental platinum. Platinum is often isolated from ores and recycled thus. Potassihloroplatinate is similarly insoluble, such that the acid has been used in the determination of potassium ions by gravimetry. Platinum(IV) oxide, PtO2, also known as Adams' Catalyst, is a black powder which is soluble in KOH solutions and concentrated acids. PtO2 and the less common PtO both decompose upon heating. Platinum also forms a trioxide, which is actually in the +4 oxidation state. Unlike palladium acetate, platinum(II) acetate is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate. The use of platinum(II) acetylacetonate has also been reported. Zeise's salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. Dichloro(cycloocta-1,5-diene)platinum(II) is a commercially available olefin complex, which contains easily displaceable cod ligands ("cod" being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry. As a soft acid, platinum has a great affinity for sulphur, such as on DMSO; numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent. Value The base value of each unit of ranges between 15 and 35Ð per unit, with up to 2 units being found at any one time. Presence on Mars: Very Rare Category:Chemical elements